telnetd.ppc-morphos 1.0

Telnet daemon, remote shell for MorphOS

Short:        Telnet daemon, remote shell for MorphOS
Author:       bfeeny@mac.com (Brian Feeny)
Uploader:     bfeeny mac com (Brian Feeny)
Type:         comm/tcp
Version:      1.0
Requires:     MorphOS 3.x, bsdsocket.library, usergroup.library (both ship with MorphOS)
Architecture: ppc-morphos
Distribution: Aminet

A telnet daemon for MorphOS - a remote shell for a platform that has never had
one.

MorphOS ships OpenSSH as a client only. There is no sshd, no telnetd, and no
working inetd, so nothing can drive the machine remotely. This fills that gap.

FEATURES

 - Authenticated login against the system's own user database, via
   usergroup.library. Accounts come from Preferences -> Users.
 - Several concurrent sessions from a single process.
 - Window size (NAWS) carried end to end, so full-screen programs know their
   geometry.
 - Starts at boot and comes back on its own after a reboot.
 - An interactive pdksh works over it, as well as the MorphOS Shell.
 - Survives idle clients, mid-command disconnects, and clients that flood
   without reading.

THERE IS NO WAY TO DISABLE AUTHENTICATION. An account with no password, or one
locked with *, is refused rather than admitted - the out-of-the-box MorphOS
state is a blank password, and failing open would hand a shell to anyone who
connects. No build of this daemon, however compiled or invoked, can serve an
unauthenticated shell.

TELNET IS A PLAINTEXT PROTOCOL. Credentials and session content cross the
network in the clear. Run it on a trusted LAN or through a tunnel, and read
doc/SECURITY.md before putting it anywhere else. This has had no outside
security review.

INSTALLATION

 Copy telnetd TO C:

 To start it at boot, put it in S:user-network-startup - NOT S:User-Startup.
 The startup-sequence never calls the network chain, so User-Startup runs
 before any interface has an address and bind() fails. The README explains
 this with the measurements behind it.

HOW IT WORKS

A telnet daemon spawns a shell and wires it to a socket. On Unix that is a
pseudo-terminal, and the Amiga lineage has no ptys. The answer is that an
AmigaDOS console is not a device node but a message port that answers packets,
so this daemon points a spawned Shell at a port it owns and answers those
packets itself. ACTION_WAIT_CHAR is select(); ACTION_SCREEN_MODE is the line
discipline.

The shell-attach layer is a standalone module with no networking in it, because
the intended second consumer is an sshd.

Full source is included, along with documentation covering the architecture, a
comparison with Unix telnetd implementations (including a candid list of what
this does not do), the prior-art survey, and the security posture.

MIT licence. Clean implementation against the MorphOS SDK headers and autodocs;
no GPL code was copied.